Wash and cut the capsicums into thin strips. Peel the garlic and cut into two. Wash and chop the carrot and celery into small pieces. Heat the olive oil in a pan and sauté the vegetables, then add the tomato paste, a little water, the capers (rinsed) and a little salt (unless the capers are already too salty). Cover and simmer on low for 30 minutes, stirring from time to time, and adding more water if necessary. Adjust with salt at the end, if necessary, and finish with some freshly chopped parsley and another drizzle of extra virgin olive oil. Serve hot or cold, with some nice crusty bread or bruschetta, or even to dress pasta.